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Question
How fast should a man of 50 kg run so that his kinetic energy be 625 J?
Solution
We have to find the speed of the running man. We have,
Mass of the man (m) = 50 kg
Kinetic energy of the man (K.E) = 325 J
So, we use the expression of kinetic energy to find the unknown quantity as,
`K.E = 1/2 mv^2`
Where,
KE - Kinetic Energy
m - Mass
v - Speed
So,
`v = sqrt((2(K.E))/((m))`
Therefore ,
`v = sqrt((2(625))/((50))` m/s
= `sqrt(25)` m/s
= 5 m/s
So , the man should be running with a speed of 5 m/s .
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